Stockton, CA (August 5, 2026) – San Joaquin County Public Health Services has confirmed a West Nile Virus (WNV) infection in San Joaquin County related to a female patient in her 60s. This is the first confirmed human case in San Joaquin County for 2026 and the 12th reported human case in California for this year.

This mosquito-borne disease was first detected in California in 2003 and now is routinely detected throughout California. It is the leading cause of mosquito-borne disease in the continental United States. According to Dr. Maggie Park, San Joaquin County Public Health Officer, “For optimal health, we encourage county residents to exercise precautions against mosquito bites, especially at dawn and dusk when mosquitos are most active. If you know you have been bitten by mosquitos and are exhibiting flu-like symptoms, you should consult with your healthcare provider, especially if you have an immunocompromised health status.”

Be aware of symptoms of serious infection such as fever, severe headaches, stiff neck, disorientation, or confusion. Seek medical attention if you believe you have been bitten and these symptoms are present. Although about 80% of those infected will not present symptoms, about 1% of those infected will develop serious symptoms. The most vulnerable populations are those with weakened immune systems, those over 60, and people with diabetes or kidney disease.

San Joaquin County residents are encouraged to follow these guidelines to protect themselves from mosquito bites and West Nile virus:

• Eliminate all sources of standing water on your property that can support mosquito development – even as little as a tablespoon.
• When outdoors, use an EPA-registered insect repellent according to label directions. Effective active ingredients include DEET, picaridin, IR3535, or oil of lemon eucalyptus. See more here.
• Avoid spending time outside when mosquitoes are most active, at dawn and dusk, and especially for the first two hours after sunset.
• Wear loose-fitting clothing with long pants and long-sleeved shirts when outdoors.
• Exclude mosquitoes from your home with tight-fitting screens on doors and windows.
• Contact your veterinarian for information on vaccinating horses against WNV.
• For mosquito problems on your property, request an inspection online on the SJC Mosquito & Vector Control District’s website: https://www.sjmosquito.org/
• Report dead birds to 1-877-WNV-BIRD (1-877-968-2473) or to westnile.ca.gov.

Contact San Joaquin County Mosquito & Vector Control District (District) at sjmosquito.org to report significant mosquito infestations or neglected (green) swimming pools. This agency also provides mosquitofish for ponds and other permanent water features. These fish feed on mosquito larvae and naturally help control mosquito populations in permanent water sources. More information about mosquitofish is found here.

The District will continue implementing the CA Mosquito-Borne Virus Surveillance and Response Plan to protect public health and welfare.

For current information on California WNV resources and statistics, visit westnile.ca.gov.

Visit the California Department of Public Health’s Mosquito Bite Toolkit here.

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